This invention relates to the ultrasonic examination of jet pump beams in nuclear reactors by an ultrasonic test apparatus including a carriage holding ultrasonic transducers, which is lowered into the "reactor" as will be discussed herein.
Certain types of nuclear reactors employ as many as twenty downwardly directed jet pumps to circulate reactor water through the core of the reactor vessel during operation. Jet pumps receive driving water from an inlet riser and through a pipe elbow connecting the inlet riser to the jet pump nozzle, as is shown for example in U.S. Pat. Nos. 3,378,456 and 3,389,055, both assigned to General Electric Company. Each pipe elbow is held in position by a jet pump beam, which will be described in substantial detail hereinafter.
The static and dynamic load on jet pump beams including vibrations imposed during reactor operation has been found to cause, in some instances, beam cracking that begins in the upper central portion of the beams. Each jet pump beam holds in place a pipe elbow, which leads reactor water from an inlet riser pipe toward a jet pump nozzle.
Cracking in a jet pump beam threatens the release of a pipe elbow from its normal position, which would impair proper jet pump operation. Accordingly, it is desirable to determine the physical integrity of jet pump beams on a regular basis, as for example by ultrasonic examination. This could be done by dismantling the jet pump beams from the reactor and transporting them to a laboratory for testing. On the other hand, the ultrasonic method and apparatus disclosed herein may instead conveniently be employed for on-site inspection of the jet pump beams within the reactor vessel.
Accordingly, it is an object of this invention to provide test apparatus for ultrasonically examining jet pump beams without requiring their removal from the reactor vessel.
Another object of this invention is to provide an ultrasonic test apparatus that eliminates the need to physically handle and transport jet pump beams for ultrasonic testing and thereby reduces radiation exposure to the personnel performing the test.